A tailplane, also known as a horizontal stabilizer, is a relatively small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplanes. The tailplane typically provides stability and control. On many aircraft, the tailplane assembly consists of a fixed surface fitted with a hinged aft surface which is called an elevator. Most airliners and transport aircraft feature a slow-moving trimmable horizontal stabilizer which is combined with one or more independently-moving elevators. The elevators are controlled by the pilot or autopilot and primarily serve to change the aircraft's attitude, while the whole assembly is used to trim (maintaining horizontal static equilibrium) and stabilize the aircraft in the pitch axis.
Conventional tailplanes are typically designed to provide a desired aerodynamic performance during certain phases of flight such as during cruise for example. However, in some flight situations, the flow conditions around tailplanes can render the elevators difficult to use by requiring a large amount of force needed to move the elevators. On aircraft that do not have fly-by-wire systems or other forms of pilot-assist actuation of the elevators, the increased amount of force required to move the elevators under those conditions must be exerted by the pilot and can consequently increase pilot workload.
Improvement is therefore desirable.